EPA Method 549.2

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EPA Method 549.2:
Diquat and Paraquat in Water Using HPLC/UV. Official Name: Determination of Diquat and Paraquat in Drinking Water by Liquid-Solid Extraction and High-Performance Liquid Chromatography with Ultraviolet Detection

A 250-mL sample, is extracted using a C-8 liquid/solid extraction (LSE) cartridge or a C-8 disk which has been specially prepared for the reversed-phase, ion-pair mode. The LSE disk or cartridge is eluted with acidic aqueous solvent to yield the eluate/extract. An ion-pair reagent is added to the eluate/extract. The concentrations of diquat and paraquat in the eluate/extract are measured using high performance liquid chromatography (HPLC) system equipped with a UV absorbance detector. A photodiode array detector is utilized to provide simultaneous detection and confirmation of the method analytes.

This method determines diquat and paraquat in drinking water sources and finished drinking water.

EPA Web site for Analytical Methods for Drinking Water

(A) Glassware contamination: Thoroughly clean glassware, including baking or solvent rinse.(B) Adsorptive loss on glass: Silanizing glassware will reduce adsorptive loss of diquat and paraquat.(C) Contamination of plastic ware: Detergent wash, rinse, and dry before use.(D) Reagent contamination: Use high purity reagents.(E) Extracted interferences: Interference from extracted non-target compounds, with retention times similar to target compounds, can be reduced by cleaning the extract. (F) Ion interferences: Ca+2 and Mg+2 lower recovery by interfering with the ion exchange process.

QC Requirements:
Initial demonstration of laboratory capability, analysis of laboratory reagent blanks (LRBs), laboratory fortified matrix samples, and laboratory fortified blanks (LFBs). Initial demonstration of laboratory capability includes analysis of LFBs at analyte concentrations of 100 ug/L. A MDL for each analyte must also be determined.

Maximum Holding Time:
7 days; extracts analyzed within 21 days.



Not specified in method. Range differs depending on matrix and instrumentation.

Precision and accuracy values were determined using single laboratory data from five replicate analyses of reagent water fortified with the analytes of interest.

MDLs were determined using the standard deviation of 5 replicate analyses of an analyte-fortified reagent water sample (2.5 ug/L of diquat and paraquat) multiplied by the t-value for 4 degrees of freedom at the 99% confidence level. Detailed instructions for how MDLs are determined are found at 40 CFR part 136, Appendix B.

Revision Number:
Revision 1.0, June 1997

Test Description:
Diquat & Paraquat -

Report Number:

Instrument used for this test: